Thanks for posting this, Mark! I stumbled across it via Google search when the RESTORE key wasn't working on my 1983 326298 board C64. I'm playing with the Hearsay 1000 voice synthesizer/recognition system for an upcoming video and it uses the RESTORE key to activate its menu. I couldn't get it to work without this mod; hadn't heard that voice in more than 30 years! :)

@Sawickipedia

3 жыл бұрын

Thanks Dave, the plan is to eventually cover this and some other simple C64 mods on the retro channel. There are a couple of c64 videos on this channel but I wanted a place for all the retro stuff, without all the other random crap that I get up to

@DrDavesDiversions

3 жыл бұрын

@@Sawickipedia Regarding this specific mod, I realized after trying it out that I installed a 47 uF cap rather than a 47 nF cap! The restore key was working,, then but I don't understand the possible negative ramifications of 1000x different capacitance in that role. So, I just removed that and installed two 100 nF caps in series (after learning some more about capacitors in series vs parallel) and that seems to work fine for the RESTORE key functionality too. Luckily I don't see any ill effects from using the wrong value for a while. (Maybe I hit the RESTORE key 30 times with that 47uF cap in parallel with the original pF cap.)

@Sawickipedia

3 жыл бұрын

Interesting, maybe I'll take a closer look at the circuit and what effects the capacitor has

@DrDavesDiversions

3 жыл бұрын

@@Sawickipedia Here are two other mods of interest, in case you want them for your video series: 326298 Reset Circuit Modification (Sun Feb 23, 2020) www.lemon64.com/forum/viewtopic.php?t=74222 hobbytronics.home.blog/tag/commodore-326298-8-pin-video/

Great Video!

Commodore intended that you would need to hit the Restore key quick, not hard, in order for it to work. This prevents accidentally triggering a Restore.

@Sawickipedia

4 жыл бұрын

I have read similar things myself, but trying to hit a key fast but with little force isn't exactly easy and I doubt that many people would have accidently hit Restore. There are rumors that certain folks at Commodore wanted to change the behaviour but it just didn't happen (at least not until the shortboard revisions).

its sad that things get released for so long before being fixed so lucky I was going to do this mod and I found a "472" 4.7nf axial ceramic capacitor is my random caps container.

What kind of witchcraft is this, how can a capacitor on the circuit board affect the physical sensitivity of a button? Its either conducting or not right?

@Sawickipedia

4 жыл бұрын

The keys themselves actually have some resistance across them when pressed, and it is slightly reduced the harder you press them. The restore key is a bit special as it actually has its own NMI line that links almost directly to the CPU. Whereas all other keys are sent to the CIA chips to decode. The bigger value cap will allow a more definite trigger for the NMI